1. Field of the Invention
The present invention relates in general to gear-shifting apparatus for an internal combustion engine and more particularly to a electronic gear-shifting circuitry for use in a high horsepower marine propulsion system for reducing the effort required to move a shift lever between reverse and neutral and between forward and neutral.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
It is well known in the art that the mechanical nature of the marine transmission used with higher horsepower marine propulsion systems, such as found in a typical outboard gear case, results in high forces when shifting the transmission out of gear under an applied drive torque. In general, the higher and smoother the applied torque, the greater the force required to shift the transmission from either reverse or forward to the neutral position. Previous systems have reduced the high shifting force necessary by reducing the applied torque to the clutch during the shifting process by killing or inhibiting the spark plug ignition. Typically in the prior art techniques a shift load activated switch simply shorts the ignition signal to ground (thereby killing the ignition). Typically with these systems, there is a noticeable time delay between the initial attempt to shift the gear and the reduction of torque such that the shifting forces are still relatively high. For example, in the prior art systems a shift force must first develop before the switch activates which, in turn, kills the ignition which, in turn, reduces the drive torque to allow clutch separation. Because of these time-sequenced events, there is, of course, a time delay which still allows significant shift forces to develop before the torque on the clutch is reduced.
It would be extremely advantageous to have a shift assist apparatus which could anticipate the upcoming shift forces or load and then proceed to reduce the drive torque load by killing the ignition before the shift load or forces at the control handle have an opportunity to build.